Through the years, play compositions of different types have been provided by practitioners in the toy arts to amuse children and adults and to aid in the development of manual skills and dexterity, as well as creativity. While the variety of such play material compositions is numerous, all generally involve the use of free-forming or malleable materials that are manipulated and shaped by the user. Certain materials have been provided which are moldable and tend to retain their shapes (e.g., modeling clay), while others are looser and more free-flowing. Others still are gels having fluid-like flow characteristics.
Regardless of the type of play compositions used, it is essential that such materials be safe for young children. Safety requirements generally mandate that play material compositions be nonirritating to the skin and eyes, and be nontoxic if ingested. Additional requirements have been expected of these materials to avoid damage to clothing, upholstery fabric, or carpeting. Conventional play compositions such as those described above typically include boron compounds such as sodium tetraborate that function as a crosslinking agent. Boron compounds, while an effective crosslinking agent, have recently come under scrutiny by some as a potential irritant when present in high concentrations. Lowering the amount of boron compounds in a composition, however, deteriorates the polymer network the compounds are intended to create. Thus, it is desirable to formulate a crosslinking system that minimizes the amount of boron compounds (and, in particular, sodium tetraborate) while providing the crosslinking properties necessary to form usable play compositions.